Introduction to Sampling and Case Selection

One of the most important decisions we make as researchers involves narrowing our substantive focus. The reasons for doing this are many. For instance,  there may be practical limitations to the scope of our projects, there may be theoretical justifications for selecting and focusing on specific cases and not others (such as research on “extreme” cases).

The lecture slides and readings below are intended to help you think about the advantages and disadvantages of the case selection methods that you choose.

Lecture by Professor Nelson on Sampling and Case Selection

General Resources

• King, Gary, Robert Owen Keohane, and Sidney Verba. 1994. Designing social inquiry: scientific inference in qualitative research. Princeton, NJ: Princeton University Press: ch. 2-4, 5.1, 6.
• Kidder, Louise H. et al. 1986. Research methods in social relations. Boston, MA: Holt, Rinehart and Winston: ch. 6, 9.

Resources on Specific Sampling Strategies

• Sudman, Seymour. “Applied Sampling.” In Handbook of Survey Research, ed. Peter Rossi, James Wright, and Andy Anderson, New York: Academic Press: 145-94
• Henry, Gary T. 1990. Practical sampling. Beverly Hills, CA:  SAGE: ch. 2
• Biernacki, P., and D. Waldorf. 1981. “Snowball sampling.” Sociological methods and research 10(2): 141–163.
• Babbie, Earl R. 1990. Survey research methods. Belmont, CA: Wadsworth Pub. Co: ch. 6.

Resources on Case Selection

• Patton, Michael Quinn. 2002. Qualitative research and evaluation methods. Beverly Hills, CA: SAGE. Beginning at page 169 is an excellent discussion of case selection strategies.
• George, Alexander L. and Timothy McKeown. 1985. “Case Studies and Theories of Organizational Decision Making.” In Robert Coulam and Richard Smith, eds., Advances in Information Processing in Organizations. Greenwich, CT.: JAI Press. 43-68.
• Kaarbo, J, and RK Beasley. 2002. A practical guide to the comparative case study method in political psychology. Political Psychology. 20(2). 369-391.
• Eckstein, H. 1975. “Case study and theory in political science.” In Handbook of political science, Reading, MA: Addison-Wesley: 79–137.
• Geddes, B. 1990. “How the cases you choose affect the answers you get: Selection bias in comparative politics.” Political analysis 2(1): 131.

Abstract: This article demonstrates how the selection of cases for study on the basis of outcomes on the  dependent variable biases conclusions. It first lays out the  logic of explanation and shows how it is violated when only cases  that have achieved the outcome of interest are studied. It then examines three well-known and highly regarded studies in the field of comparative politics, comparing the conclusions reached in  the original work with a test of the arguments on cases selected without regard for their position on the dependent variable. In  each instance,  conclusions based on the uncorrelated sample differ from the original conclusions.

Advanced Resources

• Collier, David, Henry E. Brady, and Jason Seawright. “”Critiques, Responses, and Trade-offs: Drawing Together the Debate” and “Sources of Leverage in Causal Inference: Toward an Alternative View of Methodology.” In Rethinking Social Inquiry: Diverse Tools, Shared Standards, eds. David Collier and Henry E. Brady, Lanham, MD: Rowman & Littlefield.
• Campbell, Donald T. “Degrees of Freedom and the Case Study.” Comparative Political Studies 8: 178-193.

updated August 3, 2017 – MN